Image forming apparatus

ABSTRACT

An image forming apparatus includes a sensor configured to detect a length of a sheet, which is placed on a platen, in a predetermined direction and a controller. The controller is configured to convert an image signal based on a conversion condition, control the image forming unit to form an image based on the converted image signal, and execute calibration in which the conversion condition is generated. The controller is configured, in a case in which the calibration is to be executed, to acquire information related to a size of a sheet on which a test chart is to be formed, select a sheet based on the information, form the test chart on the selected sheet acquire reading data output from the reader, and generate the conversion condition based on the reading data.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to an image forming apparatus having afunction of adjusting a printing condition and a function of diagnosingan image failure.

Description of the Related Art

An electrophotographic image forming apparatus has functions of, forexample, adjusting a printing condition and diagnosing an image failureby creating a test chart and reading the test chart by a reading device.Such an adjustment of the printing condition includes, for example,maximum density correction, tone correction, in-plane density unevennesscorrection, alignment correction (front-back registration adjustment),print head longitudinal unevenness adjustment (adjustment of lightemitter), and transfer output adjustment (secondary transfer voltageadjustment). The image failure includes, for example, a point and astreaked image. The test chart is formed in such a manner that a testimage corresponding to adjustment details and diagnosis details isprinted on a sheet.

The tone correction is described as an example of the adjustment of theprinting condition through use of the test chart. Tone characteristics(density characteristics) of an image formed on the sheet by the imageforming apparatus fluctuate due to a variation of a variety of factors.For example, the tone characteristics fluctuate due to a change of anenvironmental condition such as an air temperature and humidity at aninstalled place of the image forming apparatus, and due to a temporalchange of a component of the image forming apparatus. Therefore, theimage forming apparatus executes calibration for maintaining the tonecharacteristics. In the calibration, first, a test image is formed onthe sheet, and a test chart for the tone correction is created. Theimage forming apparatus reads the test chart by the reading device, tothereby acquire an image density of the test image. The image formingapparatus creates a correction table for enabling the acquired imagedensity to become a target density. At the time of image formation, thetone correction is carried out by using this correction table. Thecorrection table is prepared for each sheet type (a basis weight, as towhether the sheet is coated, and as to whether the sheet is recycledpaper).

In U.S. Pat. No. 9,560,229 (B2), there is proposed a method for reducinga user's workload at the time of calibration by reading a test chartthrough use of an automatic original conveying device. In JapanesePatent Application Laid-open No. 2016-103063, there is proposed a methodfor improving user's ease of use by determining whether or not a sheetfor use in the calibration is set in a cassette before the test chart iscreated. Each of the methods is a technology for improving workabilityat the time of calibration. In Japanese Patent Application Laid-open No.2003-134287, there is proposed a technology involving determiningwhether or not sheets corresponding to sizes of a plurality of originalsdifferent in size are set in cassettes and selecting whether or not tocontinue reading the originals at the time of sequentially reading theoriginals to perform copy processing.

In the case of adjusting the printing condition and diagnosing the imagefailure by using the test chart, the user is required to perform work ofsetting the test chart in the reading device. This work may cause a workerror because a manual operation is required. For example, the user mayset an original other than the test chart on the reading device in somecases. Further, in other cases, the user instructs the reading device toread the test chart without correctly setting the test chart on thereading device.

As described above, the work error includes an error in type of theoriginal to be set on the reading device and an error in way of settingthe original. No work error occurs when the original is the test chartand is set at a fixed position. Even when the original is the testchart, in the case where the original is not set at the fixed position,a reading error may occur due to the work error. In a case where theoriginal is other than the test chart, and the original is different insize from the test chart, the reading error may occur due to the workerror no matter whether the original is set at the fixed position. In acase where the original is other than the test chart, and the originalis the same in size as the test chart, the reading error may occur dueto the work error no matter whether the original is set at the fixedposition.

When the reading error occurs, the image forming apparatus instructs theuser to read the test chart again. That is, in a case where the testchart is not correctly set on the reading device, the image formingapparatus forces the user to perform work again after performing imagereading processing once, and wasteful work occurs. Therefore, atechnology for preventing the reading error due to the work error of theuser to achieve an improvement of efficiency of the work is required.Accordingly, it is a main object of the present disclosure to provide animage forming apparatus capable of preventing a reading error caused bya work error of a user.

SUMMARY OF THE INVENTION

An image forming apparatus according to the present invention includes:a reader having a platen; an image forming unit configured to form animage; a sensor configured to detect a length of a sheet, which isplaced on the platen, in a predetermined direction; and a controllerconfigured to: convert an image signal based on a conversion condition;control the image forming unit to form an image based on the convertedimage signal; and execute calibration in which the conversion conditionis generated, wherein the controller is configured, in a case where thecalibration is to be executed, to: acquire information related to a sizeof a sheet on which a test chart is to be formed; select a sheet basedon the information; control the image forming unit to form the testchart on the selected sheet; acquire a detection result of the sensor;determine whether to allow execution of a reading operation of thereader based on the detection result of the sensor and the information;acquire reading data output from the reader when the reading operationis executed; and generate the conversion condition based on the readingdata.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an image forming apparatusaccording to at least one embodiment of the present disclosure.

FIG. 2A and FIG. 2B are explanatory diagrams of a document scanner.

FIG. 3 is an explanatory table for determining original sizes.

FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are explanatory diagrams of anADF 220.

FIG. 5 is an explanatory table for determining the original sizes.

FIG. 6 is an explanatory diagram of a printer controller.

FIG. 7 is a flowchart for illustrating calibration processing.

FIG. 8A, FIG. 8B, and FIG. 8C are exemplary illustrations of screens tobe displayed on a display.

FIG. 9 is an exemplary illustration of test charts.

FIG. 10 is a flowchart for illustrating calibration processing.

FIG. 11A and FIG. 11B are exemplary illustrations of screens to bedisplayed on the display.

FIG. 12A, FIG. 12B, FIG. 12C, and FIG. 12D are exemplary illustrationsof screens to be displayed on the display.

FIG. 13A, FIG. 13B, and FIG. 13C are flowcharts for illustratingcalibration processing.

FIG. 14 is an explanatory diagram for determining whether or not it ispossible to start reading.

FIG. 15A, FIG. 15B, FIG. 15C, FIG. 15D, FIG. 15E, and FIG. 15F areexemplary illustrations of states in which the test chart is set on anoriginal tray.

FIG. 16 is a table for showing a relationship between the set states ofthe test chart and results of reading the test chart.

FIG. 17A, FIG. 17B, FIG. 17C, FIG. 17D, FIG. 17E, and FIG. 17F areexemplary illustrations of states in which the test chart is set on anoriginal table glass.

FIG. 18A and FIG. 18B are exemplary illustrations of notificationscreens.

FIG. 19A and FIG. 19B are explanatory diagrams of test charts fordensity unevenness correction.

FIG. 20 is an explanatory table for determining whether or not it ispossible to start reading.

FIG. 21 is a table for showing a relationship between the set states ofthe test chart and results of reading the test chart.

FIG. 22A and FIG. 22B are explanatory diagrams of a test chart for imagediagnosis.

FIG. 23 is a table for showing a relationship between a streak detectionposition and a cause of a streak.

FIG. 24 is an explanatory table for determining whether or not it ispossible to start reading.

DESCRIPTION OF THE EMBODIMENTS

Now, at least one embodiment of the present disclosure is described withreference to the accompanying drawings.

Image Forming Apparatus

FIG. 1 is a configuration diagram of an image forming apparatus of atleast one embodiment. An image forming apparatus 100 includes: a reader200, which is a reading device configured to read an image from anoriginal (sheet); and a printer 300 configured to form the image on asheet. The reader 200 includes a document scanner 210 and an automaticdocument feeder (hereinafter referred to as “ADF”) 220. The documentscanner 210 is provided on the printer 300, and the ADF 220 is providedon the document scanner 210. The reader 200 reads an image printed onthe original 101, and transmits an image signal, which represents theread image, to the printer 300. The printer 300 can perform imageformation processing for the sheet based on the image signal acquiredfrom the reader 200. Moreover, the printer 300 can also perform theimage formation processing for the sheet based on image data (imagesignal) transferred from an external device (a personal computer or aserver).

In FIG. 1, a direction of conveyance of the sheet by the image formingapparatus 100 is defined as a PX-direction, and a directionperpendicular to the PX-direction is defined as a Y-direction. Moreover,a direction of paper feeding by the ADF 220 is defined as anSX2-direction, and a moving direction of a first mirror unit 104 a and asecond mirror unit 104 b included in the document scanner 210 is definedas an SX1-direction.

The reader 200 reads an original fed by the ADF 220, and the original101 placed on an original table glass 102 (platen) provided on a side ofthe document scanner 210 that is close to the ADF 220. The documentscanner 210 includes therein a reader image processor 108. The readerimage processor 108 converts an electrical signal, which is generated byreading the original 101, into an image signal, and transmits the imagesignal to the printer 300.

The printer 300 includes therein a printer controller 109. The printercontroller 109 acquires the image signal from the reader image processor108 of the document scanner 210. The printer controller 109 forms theimage on a sheet based on the acquired image signal. For imageformation, the printer 300 includes image forming units 120, 130, 140,and 150, an exposure device 110, a transfer belt 111, and a fixingdevice 114.

The image forming units 120, 130, 140, and 150 are only different incolors of images to be formed, and have similar configurations toperform similar operations. The image forming unit 120 forms a yellow(Y) image. The image forming unit 130 forms a magenta (M) image. Theimage forming unit 140 forms a cyan (C) image. The image forming unit150 forms a black (K) image. Description is here given of theconfiguration of the image forming unit 120, and description of theconfigurations of other image forming units 130, 140, and 150 isomitted.

The image forming unit 120 includes a photosensitive drum 121, acharging device 122, a developing device 123, a transfer blade 124, anda surface electrometer 125. The photosensitive drum 121 is a drum-shapedphotosensitive member having a surface with a photosensitive layer. Thephotosensitive drum 121 rotates in the clockwise direction of FIG. 1.The charging device 122 uniformly charges the surface of the rotatingphotosensitive drum 121 at a predetermined potential. On the surface ofthe photosensitive drum 121, an electrostatic latent image is formed byscanning the charged surface with a laser beam by the exposure device110. The exposure device 110 is controlled by the printer controller109, and applies the laser beam to the photosensitive drum 121. Theexposure device 110 scans the photosensitive drum 121 in theY-direction. Therefore, the Y-direction corresponds to a main scanningdirection. The printer controller 109 modulates the laser beam, which isemitted from the exposure device 110, based on a pulse width modulation(PWM) signal that is based on the image signal. The developing device123 develops the electrostatic latent image through use of a developer(for example, toner) of a corresponding color (yellow in this case), andforms a toner image on the surface of the photosensitive drum 121.

The transfer blade 124 is provided opposite to the photosensitive drum121 such that the transfer belt 111 is positioned between the transferblade 124 and the photosensitive drum 121. The transfer belt 111 conveysa sheet fed from a sheet feeding cassette 152. The transfer belt 111discharges electricity to transfer the toner image formed on thephotosensitive drum 121 onto the sheet conveyed by the transfer belt111. In this manner, a yellow toner image is formed on the sheet.

Similarly, a magenta toner image is formed on a photosensitive drum 131of the image forming unit 130. A cyan toner image is formed on aphotosensitive drum 141 of the image forming unit 140. A black tonerimage is formed on a photosensitive drum 151 of the image forming unit150. The magenta toner image formed on the photosensitive drum 131 istransferred in superimposition onto the yellow toner image on the sheet.The cyan toner image formed on the photosensitive drum 141 istransferred in superimposition onto the yellow and magenta toner imageson the sheet. The black toner image formed on the photosensitive drum151 is transferred in superimposition onto the yellow, magenta, and cyantoner images on the sheet. The toner images of the four colors aretransferred in superimposition, and thus full-color toner images areformed on the sheet.

The sheet having the full-color toner images formed thereon is conveyedto the fixing device 114 by the transfer belt 111. The fixing device 114fixes the transferred toner images to the sheet. For example, the fixingdevice 114 heats and melts the toner images and applies pressure theretoto fix the toner images to the sheet. In this manner, an image is formedon the sheet. The sheet having the image formed thereon is discharged tothe outside of the printer 300.

Surface electrometers 125, 135, 145, and 155 of the image forming units120, 130, 140, and 150 measure surface potentials of the photosensitivedrums 121, 131, 141, and 151, respectively. Contrast potentials areadjusted based on results of measurement by the surface electrometers125, 135, 145, and 155.

Document Scanner

FIG. 2A and FIG. 2B are explanatory diagrams of the document scanner210. In FIG. 2A, a configuration of the document scanner 210 isillustrated. FIG. 2B is a diagram of the document scanner 210 whenviewed from the ADF 220. In a housing of the document scanner 210, thedocument scanner 210 includes a first mirror unit 104 a, a second mirrorunit 104 b, an image sensor 105, a lens 115, a motor 116, an originalsize detection sensor 113, and a home position sensor 106. The firstmirror unit 104 a includes a lamp 103 and a first mirror 107 a. Thesecond mirror unit 104 b includes a second mirror 107 b and a thirdmirror 107 c. The first mirror unit 104 a and the second mirror unit 104b are movable in the SX1-direction by being driven by the motor 116.

The document scanner 210 can perform image reading in accordance with afirst reading mode of reading the original 101 to be conveyed by the ADF220 and a second reading mode of reading the original 101 placed on theoriginal table glass 102. The first reading mode may be referred to as“flow reading” and “ADF reading”. The second reading mode may bereferred to as “fixed reading” and “original table reading”.

The first reading mode includes two types of reading systems which are asheet-through system and an original fixing system.

In the sheet-through system, through the rotation of the motor 116, thefirst mirror unit 104 a and the second mirror unit 104 b move to a flowreading position and stop. The flow reading position is a readingposition at the time of reading the image from the original 101 that isbeing conveyed by the ADF 220. The image sensor 105 reads the image ofthe original 101 during a period in which the ADF 220 is conveying theoriginal 101 on the original table glass 102.

The document scanner 210 turns on the lamp 103, and applies light to areading surface (surface on which an image is printed) of the original101. The first mirror 107 a, the second mirror 107 b, and the thirdmirror 107 c polarize reflected light (image light) of the appliedlight, which is reflected by the original 101, and guide the polarizedlight to the lens 115. The lens 115 forms an image from the image lightonto a light receiving surface of the image sensor 105. The image sensor105 converts the image light into an electrical signal. The reader imageprocessor 108 acquires the electrical signal from the image sensor 105,and generates an image signal. At the time of reading the image, thefirst mirror unit 104 a, the second mirror unit 104 b, the image sensor105, and the reader image processor 108 operate as described above.Those operations at the time of reading are the same regardless of thereading modes and the reading systems.

In the original fixing system, the ADF 220 conveys the original 101 ontothe original table glass 102, and stops the original 101 at apredetermined position on the original table glass 102. The first mirrorunit 104 a and the second mirror unit 104 b read the image of theoriginal 101 while moving in the SX1-direction by the motor 116. Afterreading the image, the ADF 220 resumes the conveyance of the original101 and discharges the original 101.

At the time of the second reading mode, through the rotation of themotor 116, the first mirror unit 104 a and the second mirror unit 104 bmove temporarily to a home position, at which the home position sensor106 is present. On the original table glass 102, one original is placedwith a reading surface thereof directed to the original table glass 102,and is positionally fixed by the ADF 220. The document scanner 210 turnson the lamp 103, and applies light to the reading surface of theoriginal 101. While moving in the SX1-direction, the first mirror unit104 a and the second mirror unit 104 b polarize the image light from theoriginal 101 by the first mirror 107 a, the second mirror 107 b, and thethird mirror 107 c, and guide the image light to the lens 115. The lens115 forms an image from the image light onto the light receiving surfaceof the image sensor 105. The image sensor 105 converts the image lightinto an electrical signal. The reader image processor 108 acquires theelectrical signal from the image sensor 105, and generates an imagesignal.

The document scanner 210 can detect the size (original size) of theoriginal 101. The document scanner 210 in at least one embodimentdetects the original size before reading such an original image. First,the document scanner 210 irradiates an end portion of the original 101by the lamp 103, and reads the reflected light from the original 101 bythe image sensor 105. The image sensor 105 is a line sensor in which,for example, a plurality of photoelectric conversion elements arearrayed in the Y-direction. The image sensor 105 reads a predeterminednumber of lines. The direction of the lines is perpendicular to theSX1-direction. A width (length in the Y-direction) of the original 101is acquired based on a result (electrical signal) of reading thepredetermined number of lines by the image sensor 105.

Moreover, the length (length in the SX1-direction) of the original 101is detected based on a detection result of the original size detectionsensor 113. At least one original size detection sensor 113 is disposedat a predetermined position in the SX1-direction in the housing of thedocument scanner 210, and detects whether or not the original 101 on theoriginal table glass 102 is present at the predetermined position. Theoriginal size detection sensor 113 is, for example, an infrared sensor,and is capable of outputting as to whether or not the original 101 ispresent in a binary manner. From a detection result of the original sizedetection sensor 113, it can be determined whether or not the original101 exceeds the position of the original size detection sensor 113 interms of length. In a case where the length of the original 101 isdesired to be detected accurately, a plurality of original sizedetection sensors 113 are disposed.

On the basis of the width and length of the original 101, which aredetected as described above, it is determined to which of a plurality ofpredetermined fixed sizes the size of the original 101 corresponds.Moreover, on the basis of the width and length of the original 101, itis also determined in which orientation (longitudinal reading or lateralreading) the original 101 is placed on the original table glass 102.

As illustrated in FIG. 2B, the original table glass 102 has an originalsize label 1230 disposed on an outer periphery thereof, and is providedwith an original registration mark 1231 at a reference abutment portionon a back side in the Y-direction. The original 101 is placed so that avertex thereof is allowed to abut against the original registration mark1231. The original registration mark 1231 serves as a reference oforiginals having the fixed sizes. The original size detection sensor 113in at least one embodiment is disposed on the back side in theY-direction of the original table glass 102 at a position a little moredistant than a length of an original having the A4 size from theoriginal registration mark 1231. Therefore, the original size detectionsensor 113 cannot detect originals 101 having the A4, B5, A5 and B6sizes, and can detect originals 101 having the A3, B4, A4R and B5Rsizes.

FIG. 3 is an explanatory table for determining original sizes. Theoriginal size is determined from combinations of the widths (detectedoriginal widths) of the originals 101, which are determined from theelectrical signals being the detection results (reading results) of theimage sensor 105, and the detection results (as to whether or not theoriginals are present) of the original size detection sensor 113. FIG. 3shows the combinations.

Though use of only the electrical signal to be output from the imagesensor 105, it is determined to which of a first group to a fourth groupthe original 101 being a detection target belongs. That is, based on thedetected original width, it is determined to which of the first group ofB5R and B6, the second group of A4R and A5, the third group of B5 andB4, and the fourth group of A4 and A3 the original 101 belongs. However,the detected original width is not enough to distinguish the sizes ineach group. It becomes possible to distinguish the sizes in each groupthrough use of the detection results (as to whether or not the originalis present) of the original size detection sensor 113. For example, whenit is determined that the size of the original 101 being a detectiontarget belongs to the fourth group based on the detected original width,it is determined that the size of the original 101 being a detectiontarget is longitudinally fed A3 when the detection result of theoriginal size detection sensor 113 indicates that the original ispresent. When the detection result indicates that the original is notpresent, it is determined that the size of the original 101 being adetection target is laterally fed A4. When the obtained determinationresult does not belong to any one of the determination results, it isdetermined that the size of the original is not a fixed size.

ADF

FIG. 4A to FIG. 4D are explanatory diagrams of the ADF 220. FIG. 4A isan exterior appearance perspective view of the ADF 220. FIG. 4B is aninternal configuration diagram of the ADF 220. FIG. 4C is a view of anoriginal stacker 301 to be described later when viewed from obliquelyabove. FIG. 4D is an internal configuration diagram of the originalstacker 301 to be described later. The ADF 220 includes the originalstacker 301, an original feeder 304, an original conveyor 308, and areverse discharge portion 313.

The original stacker 301 includes an original tray 302. On the originaltray 302, one or more originals 101 can be stacked on a stacking surfacethereof. The original tray 302 functions as a feeder. The originalstacker 301 is provided with an original indicator 303 configured toturn on when the originals 101 are stacked on the original tray 302. Theoriginals 101 stacked on the original tray 302 are conveyed one by oneonto the original table glass 102 by the original feeder 304, pass onthe original table glass 102, and are discharged to a discharge tray 321of the reverse discharge portion 313 by the reverse discharge portion313.

In the original feeder 304, a pickup roller 306, a feed roller 307 and aregistration roller pair 305 are provided along a conveying path of theoriginals 101. The pickup roller 306 is a roller that is rotatable andvertically movable. At the time of feeding the originals 101, the pickuproller 306 is lowered on an uppermost original 101 of an original bundlestacked on the original tray 302 to be brought into contact with thisoriginal 101, and conveys this original 101. The feed roller 307 conveyssuch originals 101, which are conveyed by the pickup roller 306, to theregistration roller pair 305. The originals 101 are conveyed one by oneby the pickup roller 306 and the feed roller 307. The registrationroller pair 305 is stopping at the time when a tip end of each original101 reaches the registration roller pair 305. This is in order tocorrect skew feeding of the original 101. The registration roller pair305 starts to rotate after correcting the skew feeding, and conveys theoriginal 101 to the original conveyor 308.

The original conveyor 308 includes a conveyor belt 309, a drive roller310, a driven roller 311, and a plurality of pressing rollers 312. Theoriginal conveyor 308 conveys the original 101 in the SX1-direction byusing the conveyor belt 309. The conveyor belt 309 is tensioned aroundthe drive roller 310 and the driven roller 311. Moreover, the conveyorbelt 309 is pressed against the original table glass 102 by the pressingrollers 312. By frictional force, the conveyor belt 309 conveys theoriginal 101 that enters between the conveyor belt 309 and the originaltable glass 102. Thus, the original 101 is conveyed on the originaltable glass 102.

In the original fixing system of the first reading mode, the conveyorbelt 309 stops when the original 101 reaches the reading position. Afterthe original 101 is read by the first mirror unit 104 a and the secondmirror unit 104 b, the conveyor belt 309 conveys the original 101 to thereverse discharge portion 313. In this case, the first mirror unit 104 aand the second mirror unit 104 b read the stopping original 101 whilemoving in the SX1-direction.

In the sheet-through system of the first reading mode, the conveyor belt309 does not stop even when the original 101 reaches the readingposition, and continues to convey the original 101. In this case, whilecontinuing to stop, the first mirror unit 104 a and the second mirrorunit 104 b read the original 101 that is being conveyed. That is,scanning of the original 101 is performed by the movement of theoriginal 101 in place of the first mirror unit 104 a and the secondmirror unit 104 b.

The reverse discharge portion 313 includes a reverse roller 314, aconveyor roller pair 315, a reverse flapper 316, a discharge flapper317, and a reverse roller 318. The reverse discharge portion 313reverses the front and back of the original 101 conveyed from theoriginal conveyor 308, and discharges the original 101 to the dischargetray 321 of a discharged sheet stacking portion 320.

At the time of entering the reverse discharge portion 313, the original101 conveyed by the conveyor belt 309 of the original conveyor 308 islifted up by the reverse flapper 316 and is conveyed to the reverseroller 314. The original 101 is disposed between the reverse roller 314that rotates counterclockwise (CCW) and the reverse roller 318 thatfaces the reverse roller 314, and is conveyed to the conveyor rollerpair 315. When a rear end of the original 101 passes through thedischarge flapper 317, the discharge flapper 317 rotates clockwise (CW).Moreover, the reverse roller 314 also rotates clockwise (CW). Thus, theoriginal 101 is conveyed in a switchback manner, and is discharged tothe discharge tray 321 of the discharged sheet stacking portion 320.

Detection of Original Size by ADF

As illustrated in FIG. 4C, on the original tray 302 of the originalstacker 301, a pair of regulating members 332 slidable in a widthdirection (Y-direction: a direction perpendicular to the conveyancedirection of the original) are disposed. The regulating members 332 havea function of aligning the position of the original in the widthdirection at the time of feeding the original, which is placed on theoriginal stacker 301 (original tray 302), by regulating both endportions of the original in the width direction. The pair of regulatingmembers 332 is movable symmetrically to each other with respect to thewidth direction of the original. The regulating members 332 regulate theposition of the original so that the center of the original in the widthdirection, which is to be fed, is matched with a feeding center.

The original stacker 301 is provided with an original width sensor 333capable of detecting the positions of the regulating members 332 (FIG.4D). The original width sensor 333 detects a size of the original in thewidth direction, which is placed on the original tray 302, by detectingthe positions of the regulating members 332 which move in accordancewith the width of the original.

On the original stacker 301, a plurality (two in at least oneembodiment) of original length detection sensors 334 a and 334 b arearranged side by side in a feeding direction (SX2-direction) of theoriginal. The original length detection sensors 334 a and 334 b detectwhether or not the original 101 is present on the original stacker 301(original tray 302). A size of the original 101 in such an originalfeeding direction (SX2-direction) of the original 101 is detected basedon a detection result of each of the original length detection sensors334 a and 334 b.

The size and orientation (whether the original is longitudinally fed orlaterally fed) of the original placed on the original stacker 301 aredetectable based on such detection results of the original width sensor333 and the original length detection sensors 334 a and 334 b. FIG. 5 isan explanatory table for determining the original sizes. Fromcombinations of the respective detection results from the original widthsensor 333 and the original length detection sensors 334 a and 334 b,the size of the original placed on the original stacker 301 (originaltray 302) is determined. FIG. 5 shows combinations of the detectedoriginal widths of the originals in the width direction on the originalstacker 301, which are detection results of the original width sensor333, and detection results of the original length detection sensors 334a and 334 b, which are as to whether or not the originals to be placedon the original stacker 301 are present in the original feedingdirection (SX2-direction). The original length detection sensors 334 aand 334 b output as to whether the originals are present by binaryvalues.

Through use of only the detection results of the original width sensor333, it is determined to which of a first group to a fourth group theoriginal 101 being a detection target belongs. That is, based on thedetected original width, it is determined to which of the first group ofB5R and B6, the second group of A4R and A5, the third group of B5 andB4, and the fourth group of A4 and A3 the original 101 belongs. However,the detected original width is not enough to distinguish the sizes ineach group. It becomes possible to distinguish the sizes in each groupthrough use of the detection results (as to whether or not the originalis present) of the original length detection sensor 334 b. For example,in a case where it is determined that the size of the original 101 beinga detection target belongs to the fourth group based on the detectedoriginal width, it is determined that the size of the original 101 beinga detection target is longitudinally fed A3 when the detection result ofthe original length detection sensor 334 b indicates that the originalis present. When the detection result indicates that the original is notpresent, it is determined that the size of the original 101 being adetection target is laterally fed A4. When detection result of theoriginal length detection sensor 334 a indicates that the original ispresent, and the obtained determination result does not belong to anyone of the determination results, it is determined that the size of theoriginal is not a fixed size. Moreover, when the original lengthdetection sensor 334 a does not detect the original, it is determinedthat the original is not present.

The original size detection as described above for the original 101placed on the original table glass 102 and the original size detectionas described above for the original 101 placed on the original tray 302are performed by the reader 200. The reader 200 performs original sizedetection processing in response to an instruction from the printer 300.The detection results of the original size are transmitted from thereader 200 to the printer 300.

Pinter Controller

FIG. 6 is an explanatory diagram of the printer controller 109. Thefollowing components are connected to the printer controller 109: acentral processing unit (CPU) 401 configured to integrally controloperations of the image forming apparatus 100; a memory 402; the reader200; and a semiconductor laser 410. The memory 402 includes a read onlymemory (ROM) and a random access memory (RAM), and stores a controlprogram for controlling the operations of the image forming apparatus100 and a variety of pieces of data. The CPU 401 executes the controlprogram stored in the memory 402, to thereby function as a controllerconfigured to control the operations of the image forming apparatus 100.

An operating unit 400 is connected to the CPU 401. The operating unit400 is a user interface including an input device and an output device.The input device includes a touch panel, and key buttons such as a startkey, a stop key, and a numeric keypad. The output device includes adisplay and a speaker. The reader 200 includes a reader controller 413as well as the reader image processor 108 described above. The readercontroller 413 performs the above-mentioned processing of determiningthe original size. The semiconductor laser 410 is provided in theexposure device 110, and emits a laser beam to be applied to thephotosensitive drums 121, 131, 141 and 151.

The printer controller 109 includes a color processor 403, a tonecontroller 411, a dither processor 407, a PWM unit 408, and a laserdriver 409. The printer controller 109 converts respective image signalsof R, G, and B into PWM signals, and performs light emission control forthe semiconductor laser 410 based on the PWM signals.

The image signals output from the reader image processor 108 of thereader 200 are input to the color processor 403. The color processor 403performs image processing and color processing on the input imagesignals so that a desired output result (image) can be obtained in acase where the printer 300 has an ideal output characteristic. The colorprocessor 403 increases the number of tone levels of the image signal to10 bits from 8 bits in order to improve the accuracy. The colorprocessor 403 includes a LUTid 404 being a look-up table. The LUTid 404is a luminance-density conversion table for converting luminanceinformation included in the image signal into density information. Thecolor processor 403 uses the LUTid 404 to convert luminance informationof the image signals of R, G, and B into density information of theimage signals of yellow (Y), magenta (M), cyan (C), and black (K). Theimage signals of Y, M, C, and K are input to the tone controller 411.

The tone controller 411 corrects tone characteristics of the imagesignals, which are acquired from the color processor 403, by usingcorrection conditions corresponding to a type of the sheet on which theimage is to be formed. For this purpose, the tone controller 411includes an under color removal (UCR) unit 405 and a y corrector 406including an LUTa being a lookup table. The tone controller 411 correctsthe tone of the image signals of Y, M, C, and K so that a desired outputresult (image) can be obtained in accordance with the actual outputcharacteristic of the printer 300. The UCR unit 405 regulates theintegrated value of the image signal in each pixel to limit the totalsum of the image signal levels. When the total sum exceeds theregulation value, the UCR unit 405 performs under color removal (UCR)processing of replacing a predetermined amount of C, M, and Y imagesignals into K image signals, to thereby reduce the total sum of theimage signal levels.

The y corrector 406 corrects density characteristics (y characteristics)of the image signals by using the LUTa. The LUTa is a 10-bit conversiontable (tone correction conditions) for correcting the densitycharacteristics. As described above, the tone characteristics of theimage to be formed on the sheet by the printer 300 vary depending on anenvironmental variation and consumption of the components. Moreover, thetone characteristics of the image differ depending on the type of thesheet. The CPU 401 updates the LUTa by executing calibration, andmaintains the tone characteristics of the image at predetermined tonecharacteristics. The printer 300 forms the image on the sheet inaccordance with the image signals corrected by the y corrector 406. Thememory 402 may hold LUTa for each type of the sheet. The CPU 401 readsan LUTa corresponding to the type of the sheet, which is designated bythe operating unit 400, from the memory 402, and sets the LUTa to the ycorrector 406. The LUTa is used at the time of copying the original andforming the image in accordance with a print job from a host computer,but is not used at the time of executing the calibration. The imagesignals of Y, M, C, and K after the tone correction are input to thedither processor 407.

The dither processor 407 performs dither processing (halftoneprocessing) on the 10-bit image signals of Y, M, C, and K subjected totone correction, to thereby convert the 10-bit image signals of Y, M, C,and K into 4-bit signals. The PWM unit 408 performs pulse widthmodulation on the signals subjected to dither processing to generate thePWM signal corresponding to the control signal for the exposure device110. The PWM signal is input to the laser driver 409. The laser driver409 controls the light emission of the semiconductor laser 410 inaccordance with the PWM signal.

Calibration

The calibration is performed by using a test chart created in theprinter 300. In the following, a method of creating the LUTa by thecalibration is described.

In order to create a test chart for the tone correction, the CPU 401supplies predetermined image signals (density signals) to the ditherprocessor 407, and forms a test image on the sheet. The sheet on whichthe test image is formed is the test chart. The reader 200 reads thetest chart, and transmits image signals (luminance signals), which arereading results, to the color processor 403. Through use of the LUTid404, the color processor 403 converts the luminance signals of red (R),green (G), and blue (B) into density signals of Y, M, C, and K. In thiscase, Y is converted into a density signal value thereof by using aluminance value of B, C is converted into a density signal value thereofby using a luminance value of B, and M and K are converted into densitysignal values thereof by using a luminance value of G. The LUTid 404 maychange the table for use in the conversion depending on the type of thesheet of the test chart. The above-mentioned color processing to beperformed by the color processor 403 at the time of the calibration isprocessing different from color processing performed in a case where anormal original is read.

Next, the CPU 401 creates the LUTa so that the density signals acquiredvia the reader 200 is the same as the density signals used to form thetest image. The LUTa is created for each color of Y, M, C, and K.

As described above, the reader 200 can read the original image in bothof the reading modes which are the ADF reading (first reading mode) andthe original table reading (second reading mode). The reader 200 mayread the test image printed on the test chart in any one of the ADFreading and the original table reading. The ADF reading may be givenpriority because a workload of the user is smaller in the ADF readingthan in the original table reading.

FIG. 7 is a flowchart for illustrating calibration processing. FIG. 8Ato FIG. 8C are illustrations of screens to be displayed on a display ofthe operating unit 400 during the calibration processing. FIG. 9 is anillustration of test charts for use in the calibration.

From the operating unit 400, the CPU 401 acquires an instruction thatindicates which reading mode between the ADF reading and the originaltable reading is selected by the user (Step S501). In a case where theADF reading is selected by the user, the CPU 401 operates in the firstreading mode. In a case where the original table reading is selected bythe user, the CPU 401 operates in the second reading mode. FIG. 8A is anexemplary illustration of an operation screen 700 a at the time ofselecting the reading mode. The CPU 401 displays the operation screen700 a on the display of the operating unit 400. On the operation screen700 a, a button 701 a allowing selection of the ADF reading and a button701 b allowing selection of the original table reading are displayed.The user selects any one of the button 701 a and the button 701 bthrough the operating unit 400, to thereby select the reading mode. Fromthe operating unit 400, the CPU 401 acquires information indicating theselected reading mode. The CPU 401 determines the selected reading mode(Step S502).

In a case where the ADF reading is selected (Step S502: Y), the CPU 401sets a first image forming condition for the printer 300, and transmitsto the dither processor 407 the density signals of the test image forcreating the test chart for the tone correction. Thus, the CPU 401causes the printer 300 to create the test chart (Step S503). At thistime, the LUTa is not used.

As illustrated in FIG. 9, each of test charts 801 a and 801 b includestest images formed of 10 tones for each color of Y, M, C, and K. Foreach color, for example, images of 10 tones are formed of densitysignals of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. Thedither processor 407 may be able to apply a plurality of procedures ofhalftone processing. For example, the dither processor 407 may include asmall number-of-line screen (160 lines per each (lpi) to 180 lpi) and alarge number-of-line screen (250 lpi to 300 lpi). The test chart 801 ais a test chart to which the small number-of-line screen is applied. Thetest chart 801 b is a test chart to which the large number-of-linescreen is applied. The small number-of-line screen is applied to aphotographic image and the like, and the large number-of-line screen isapplied to a character and the like. In a case where the printer 300 hasan ability to form an image with three types or more of the number oflines, the number of test charts may be three or more. In this case, thenumber of test charts is defined to be one for the sake of convenience.

After creating the test chart, the CPU 401 causes the reader 200 tooperate the ADF 220, and executes the ADF reading (Step S504). For thispurpose, the CPU 401 displays, on the display of the operating unit 400,a message for urging the user to place the test chart on the originaltray 302 of the ADF 220. FIG. 8B is an exemplary illustration of such amessage screen 700 b. On the message screen 700 b, the message forurging the user to place the test chart on the original tray 302 and abutton 701 c for issuing an instruction to start the reading aredisplayed.

After placing the test chart on the original tray 302, the user pressesthe button 701 c through the operating unit 400, to thereby issue aninstruction to start the ADF reading. Thus, the CPU 401 acquires fromthe operating unit 400 such an instruction to start the reading in theADF reading. When acquiring the instruction to start the reading, theCPU 401 instructs the reader 200 to perform the ADF reading. The reader200 conveys the test chart by the ADF 220, and reads the test chart bythe document scanner 210. The reader image processor 108 of the documentscanner 210 transmits a luminance signal, which indicates a readingresult of the test chart, to the printer controller 109.

In a case where the original table reading is selected (Step S502: N),the CPU 401 sets a second image forming condition for the printer 300,and transmits to the dither processor 407 the density signals of thetest image for creating the test chart for the tone correction. Thus,the CPU 401 causes the printer 300 to create the test chart (Step S511).At this time, the LUTa is not used. Examples of the test images of thetest charts are illustrated in FIG. 9, and are the same as those in thecase of the ADF reading.

After creating the test chart, the CPU 401 executes the original tablereading by the reader 200 (Step S512). For this purpose, the CPU 401displays, on the display of the operating unit 400, a message for urgingthe user to place the test chart on the original table glass 102. FIG.8C is an exemplary illustration of such a message screen 700 c. On themessage screen 700 c, the message for urging the user to place the testchart on the original table glass 102 and the button 701 c for issuingan instruction to start the reading are displayed.

The user opens the ADF 220 to expose the original table glass 102, andplaces, on the original table glass 102, the test chart with a surfaceon which the test screen is formed directed to the original table glass102. The user thereafter presses the button 701 c through the operatingunit 400, to thereby issue an instruction to start the original tablereading. Thus, the CPU 401 acquires from the operating unit 400 such aninstruction to start the reading in the original table reading. Whenacquiring the instruction to start the reading, the CPU 401 instructsthe reader 200 to perform the original table reading. The reader 200reads the test chart on the original table glass 102 by the documentscanner 210. The reader image processor 108 of the document scanner 210transmits a luminance signal, which indicates a reading result of thetest chart, to the printer controller 109.

When the test chart is read by the processing of Step S504 and StepS512, the CPU 401 acquires the density signals of the test image basedon the reading result (luminance signals) (Step S505). The CPU 401converts the luminance signals into the density signals by using theLUTid 404 of the color processor 403. Thus, a density signal for each ofthe images of 10 tones is obtained. The CPU 401 may switch the tables ofthe LUTid 404 of the color processor 403 depending on the type of thesheet for use in the test chart.

The CPU 401 creates the LUTa based on the density signals used to createthe test image and the density signals obtained from the reading resultof the test chart (Step S506). The CPU 401 stores the created LUTa inthe memory 402. The calibration processing is performed as describedabove when the test image is formed on the single sheet and the testchart is single.

The calibration processing is performed as follows in a case where thetest image is formed on two sheets and the test chart is two. FIG. 10 isa flowchart for illustrating the calibration processing in this case.The same step numbers are assigned to the same processing as theprocessing of FIG. 7. A description of the same processing is omitted.FIG. 11A and FIG. 11B and FIG. 12A to FIG. 12D are exemplaryillustrations of screens to be displayed on the display of the operatingunit 400 during the calibration processing.

As described above, the dither processor 407 may include a plurality ofscreens different in number of lines from each other. Tonecharacteristics of images formed based on the different numbers of linessometimes differ greatly from each other. In such a case, the LUTa iscreated for each number of lines. However, it is difficult for the userto determine the number of lines with which the screen is to becalibrated. This is because it is difficult for the user to specify thenumber of lines applied to an image of a character, a line, aphotograph, or the like and the number of lines applied to copying.Therefore, in a case where the screens with a plurality of pieces of thenumber of lines are provided, a load on the user is reduced in such amanner that the calibration is executed for the screens with all piecesof the number of lines. The calibration in the case in which the numberof test charts is two is applied to such a case.

In a case where the ADF reading is selected as the reading mode (StepS502: Y), the CPU 401 continuously creates the two test charts 801 a and801 b by the printer 300 (Step S903). The CPU 401 displays a messagescreen 700 d, an example of which is illustrated in FIG. 11A, on thedisplay of the operating unit 400. On the message screen 700 d, thereare displayed: a message for urging the user to confirm whether two ormore sheets are housed in the sheet feeding cassette 152; a messageindicating that two test charts are continuously created; and a button701 d for issuing an instruction to start printing. After confirmingthat two or more sheets are housed in the sheet feeding cassette 152,the user presses the button 701 d through the operating unit 400, tothereby issue an instruction to start the printing. Thus, the CPU 401acquires from the operating unit 400 such an instruction to start theprinting.

When acquiring the instruction to start the printing, the CPU 401 sets afirst screen on the dither processor 407, and transmits to the ditherprocessor 407 the density signals of the test image for creating thetest chart for the tone correction. The dither processor 407 uses thefirst screen to convert the 10-bit density signals into 4-bit densitysignals. The printer 300 creates the test chart 801 a based on the 4-bitdensity signals. Next, the CPU 401 sets a second screen on the ditherprocessor 407, and transmits to the dither processor 407 the densitysignals of the test image for creating the test chart for the tonecorrection. The dither processor 407 uses the second screen to convertthe 10-bit density signals into 4-bit density signals. The printer 300creates the test chart 801 b based on the 4-bit density signals.

After creating the test chart, the CPU 401 causes the reader 200 tooperate the ADF 220, and executes the ADF reading for the two testcharts 801 a and 801 b (Step S904). For this purpose, the CPU 401displays, on the display of the operating unit 400, a message for urgingthe user to place the two test charts 801 a and 801 b on the originaltray 302 of the ADF 220. FIG. 11B is an exemplary illustration of such amessage screen 700 e. On the message screen 700 e, there are displayed:a message for urging the user to stack the test chart 801 b of thesecond screen on the test chart 801 a of the first screen and place thetest charts 801 a and 801 b on the original tray 302; and the button 701c for issuing an instruction to start the reading. The printer 300 mayprint a message or a mark, which indicates which of the screens isapplied, on the test charts 801 a and 801 b.

After placing the test chart on the original tray 302, the user pressesthe button 701 c through the operating unit 400, to thereby issue aninstruction to start the ADF reading. Thus, the CPU 401 acquires fromthe operating unit 400 such an instruction to start the reading in theADF reading. When acquiring the instruction to start the reading, theCPU 401 instructs the reader 200 to perform the ADF reading. The reader200 continuously conveys the test charts 801 a and 801 b by the ADF 220,and continuously reads the test charts 801 a and 801 b by the documentscanner 210. The reader image processor 108 of the document scanner 210transmits a luminance signal, which indicates reading results of thetest charts 801 a and 801 b, to the printer controller 109.

In a case where the original table reading is selected as the readingmode (Step S502: N), the CPU 401 creates the first test chart 801 a bythe printer 300 (Step S911). The CPU 401 displays a message screen 700f, an example of which is illustrated in FIG. 12A, on the display of theoperating unit 400. On the message screen 700 f, there are displayed: amessage for urging the user to confirm whether two or more sheets arehoused in the sheet feeding cassette 152; a message indicating that thefirst test chart is created; and a button 701 d for issuing aninstruction to start printing. After confirming that two or more sheetsare housed in the sheet feeding cassette 152, the user presses thebutton 701 d through the operating unit 400, to thereby issue aninstruction to start the printing. Thus, the CPU 401 acquires from theoperating unit 400 such an instruction to start the printing.

When acquiring the instruction to start the printing, the CPU 401 setsthe first screen on the dither processor 407, and transmits to thedither processor 407 the density signals of the test image for creatingthe test chart for the tone correction. The dither processor 407 usesthe first screen to convert the 10-bit density signals into 4-bitdensity signals. The printer 300 creates the first test chart 801 abased on the 4-bit density signals.

After creating the first test chart 801 a, the CPU 401 executes theoriginal table reading of the first test chart 801 a by the reader 200(Step S912). For this purpose, the CPU 401 displays, on the display ofthe operating unit 400, a message for urging the user to place the testchart on the original table glass 102. FIG. 12B is an exemplaryillustration of such a message screen 700 g. On the message screen 700g, the message for urging the user to place the first test chart 801 aon the original table glass 102 and the button 701 c for issuing aninstruction to start the reading are displayed.

The user opens the ADF 220 to expose the original table glass 102, andplaces, on the original table glass 102, the first test chart 801 a witha surface on which the test screen is formed directed to the originaltable glass 102. The user thereafter presses the button 701 c throughthe operating unit 400, to thereby issue an instruction to start theoriginal table reading. Thus, the CPU 401 acquires from the operatingunit 400 such an instruction to start the reading in the original tablereading. When acquiring the instruction to start the reading, the CPU401 instructs the reader 200 to perform the original table reading. Thereader 200 reads the first test chart 801 a on the original table glass102 by the document scanner 210. The reader image processor 108 of thedocument scanner 210 transmits a luminance signal, which indicates areading result of the first test chart 801 a, to the printer controller109.

Subsequently, the CPU 401 causes the printer 300 to create the secondtest chart 801 b (Step S913). The CPU 401 displays a message screen 700h, an example of which is illustrated in FIG. 12C, on the display of theoperating unit 400. On the message screen 700 h, a message indicatingthat the second test chart is to be created and a button 701 d forissuing an instruction to start the printing are displayed. The userpresses the button 701 d through the operating unit 400, to therebyissue an instruction to start the printing. Thus, the CPU 401 acquiresthe instruction to start printing from the operating unit 400.

When acquiring the instruction to start the printing, the CPU 401 setsthe second screen on the dither processor 407, and transmits to thedither processor 407 the density signals of the test image for creatingthe test chart for the tone correction. The dither processor 407 usesthe second screen to convert the 10-bit density signals into 4-bitdensity signals. The printer 300 creates the second test chart 801 bbased on the 4-bit density signals.

After creating the second test chart 801 b, the CPU 401 executes theoriginal table reading of the second test chart 801 b by the reader 200(Step S914). For this purpose, the CPU 401 displays, on the display ofthe operating unit 400, a message for urging the user to place the testchart on the original table glass 102. FIG. 12D is an exemplaryillustration of such a message screen 700 i. On the message screen 700i, the message for urging the user to place the second test chart 801 bon the original table glass 102 and the button 701 c for issuing aninstruction to start the reading are displayed.

The user opens the ADF 220 to expose the original table glass 102, andplaces, on the original table glass 102, the second test chart 801 bwith a surface on which the test screen is formed directed to theoriginal table glass 102. The user thereafter presses the button 701 cthrough the operating unit 400, to thereby issue an instruction to startthe original table reading. Thus, the CPU 401 acquires from theoperating unit 400 such an instruction to start the reading in theoriginal table reading. When acquiring the instruction to start thereading, the CPU 401 instructs the reader 200 to perform the originaltable reading. The reader 200 reads the second test chart 801 b on theoriginal table glass 102 by the document scanner 210. The reader imageprocessor 108 of the document scanner 210 transmits a luminance signal,which indicates a reading result of the second test chart 801 b, to theprinter controller 109.

When the reading of the two test charts 801 a and 801 b is completed,the CPU 401 acquires the density signals of the test image based on thereading results (luminance signals) (Step S505). The CPU 401 creates theLUTa based on the density signals used to create the test image and thedensity signals obtained from the reading result of the test charts(Step S506). The CPU 401 creates LUTa′ based on the reading result ofthe test chart 801 a, and creates LUTa” based on the reading result ofthe test chart 801 b.

An example of forming the two test charts 801 a and 801 b is describedabove. However, the calibration may be performed by using three or moretest charts. Every time when the test charts are increased by one, theprocessing of Step S913 and Step S914 is added.

Determination as to Whether to Start Reading Test Chart

In at least one embodiment, before the test chart is read, it isdetermined whether or not the test chart is set correctly, and it isdetermined whether or not it is possible to start reading the test chartby the reader 200 based on a determination result. Specifically, onlywhen the test chart is set correctly, the reader 200 is allowed to readthe test chart. The statement “test chart is set correctly” means thatthe test chart being a sheet on which the test image is printed isplaced on a correct position of the original tray 302 or the originaltable glass 102. The reader 200 is allowed to read the test chart onlywhen the test chart is set correctly, and thus a reading error of thetest chart is prevented from occurring. That is, it is determinedwhether or not the test chart is set correctly before the test chart isread, and thus it is determined whether or not it is possible to startreading the test chart. FIG. 13A to FIG. 13C are flowcharts forillustrating calibration processing including the determination as towhether or not to start the reading.

FIG. 13A is a flowchart for illustrating processing for determiningwhether or not it is possible to start reading the test chart at atiming before receiving the instruction to start reading the test chart.

The CPU 401 acquires information indicating the size (sheet size) of thesheet, which is selected by the user when the test chart is created(Step S101). In this case, the case in which the user selects a sheet ofthe A4 size is described. As described above, before the test chart iscreated, the user selects the reading mode of the test chart from theADF reading (first reading mode) and the original table reading (secondreading mode). After the reading mode is selected through the operationscreen 700 a of FIG. 8A, the CPU 401 displays a screen for selecting thesheet size, for example, on the display of the operating unit 400. Thus,subsequently to the selection of the reading mode, the user can selectthe sheet size of the sheet for use in the test chart from the screenfor selecting the sheet size. Moreover, the orientation of the sheet maybe selected when the sheet size is selected. In this case, the CPU 401also acquires information indicating the orientation of the sheet.

The CPU 401 creates the test chart by using the sheet of the sheet sizeselected by the user (Step S102). The CPU 401 stores the sheet size ofthe sheet used to create the test chart in the memory 402. In a casewhere the orientation of the sheet is also selected, the informationindicating the orientation of the sheet is also stored in the memory402. As described above, after the test chart is created, the test chartis read in the reading mode selected by the user. For this purpose, theuser inputs the instruction to start the reading through the operatingunit 400. In a case where the ADF reading (first reading mode) isselected, the CPU 401 displays a message, which urges the user to setthe test chart on the original tray 302 and to adjust an intervalbetween the regulating members 332, on the display of the operating unit400. In a case where the original table reading (second reading mode) isselected, the CPU 401 displays on the display of the operating unit 400a message for urging the user to place the test chart with the use ofthe original registration mark 1231 of the original table glass 102 as areference.

The CPU 401 detects the original size (size of the set test chart) bythe reader 200 (Step S103). In the case of the ADF reading (firstreading mode), the reader controller 413 always continues to update thedetection result of the original size based on the detection results ofthe original width sensor 333 during a period in which the originallength detection sensors 334 a and 334 b are detecting the originals.This is because the user adjusts the positions of the regulating members332 and sets the test chart at a correct position under a state in whichthe user places the test chart on the original stacker 301. In the caseof the original table reading (second reading mode), the readercontroller 413 detects the original size at a timing of closing thereader 200. This is because, at the time when the user sets the testchart on the original table glass 102, operations of opening and closingthe reader 200 accompany the setting.

The CPU 401 compares the sheet size of the test chart created by theprocessing of Step S102, the sheet size being acquired by the processingof Step S101, and the sheet size detected by the processing of Step S103with each other, and determines whether or not the sheet size and theoriginal size are the same as each other based on a result of thecomparison (Step S104). In a case where the sheet size and the originalsize are the same as each other, the CPU 401 determines that the testchart is set correctly, and determines that it is possible to start thereading. In a case where the sheet size and the original size are notthe same as each other (Step S104: N), the CPU 401 repeats theprocessing of Step S103 and Step S104 until the original size is thesame as the sheet size of the test chart.

FIG. 14 is an explanatory table for determining whether or not it ispossible to start the reading. In this case, the test chart is createdby using the sheet of the A4 size. Therefore, the CPU 401 determinesthat the sheet size and the original size are the same as each other ina case where the original size detected by the reader 200 is the A4 orthe A4R, and determines that the sheet size and the original size arenot the same as each other in a case where the sheet size thus detectedis other than the A4 and the A4R. In a case where the test chart iscreated by using a sheet of the A3 size, the CPU 401 determines that thesheet size and the original size are the same as each other only whenthe original size detected by the reader 200 is A3.

FIG. 15A to FIG. 15F are exemplary illustrations of states in which thetest chart is set on the original tray 302 at the time of the ADFreading. FIG. 16 is a table for showing a relationship between the setstates of the test chart on the original tray 302 and results of readingthe test chart. In this case, the case in which the test chart iscreated by using the sheet of the A4 size is illustrated as an example.

In FIG. 15A, the case in which the test chart is set correctly isillustrated. The test chart is set so that the center in the widthdirection of the original to be fed and the center of the test chart arematched with each other. The pair of regulating members 332 has moved tothe size positions of the original width of the test chart. In thiscase, the CPU 401 determines that it is possible to start reading thetest chart. In FIG. 15B, the case in which the test chart is setcorrectly in the lateral reading direction (rotated (R) orientation) isillustrated. In this case, the detected original size is the same sizeas that of the created test chart, and hence the CPU 401 determines thatit is possible to start reading the test chart.

In FIG. 15C, the case in which the test chart is set on a front side inthe width direction is illustrated. In this case, the test chart is notset correctly, and the created test chart and the detected original sizeare not the same as each other. Thus, the CPU 401 determines that it isnot possible to start reading the test chart. Therefore, an occurrenceof a reading error is prevented. In FIG. 15D, the case in which the testchart is set obliquely with respect to the conveyance direction isillustrated. In this case, the test chart is not set correctly, and thecreated test chart and the original size are not the same as each other.Thus, the CPU 401 determines that it is not possible to start readingthe test chart. Therefore, the occurrence of the reading error isprevented.

In FIG. 15E, the case in which an original different from the createdtest chart is set and a detected size of the original is different fromthe sheet size of the test chart is illustrated. In this case, the CPU401 determines that it is not possible to start reading the test chart.Therefore, the occurrence of the reading error is prevented. In FIG.15F, the case in which an original different from the created test chartis set and a detected size of the original is the same as the sheet sizeof the test chart is illustrated. In this case, the CPU 401 determinesthat it is possible to start reading the test chart. However, thereading error occurs after the original is read.

FIG. 17A to FIG. 17F are exemplary illustrations of states in which thetest chart is set on the original table glass 102 at the time of theoriginal table reading.

In FIG. 17A, the case in which the test chart is set correctly isillustrated. The test chart is placed while a sheet end portion of thetest chart is being registered with the original registration mark 1231of the reference abutment portion on a depth side of the original tableglass 102. In this case, the CPU 401 determines that it is possible tostart reading the test chart. In FIG. 17B, the case in which the testchart is set correctly in the lateral reading direction (rotated (R)orientation) is illustrated. In this case, the detected original size isthe same size as that of the created test chart, and hence the CPU 401determines that it is possible to start reading the test chart.

In FIG. 17C, the case in which the test chart is not set while the sheetend portion of the test chart is being registered with the originalregistration mark 1231 is illustrated. In this case, the test chart isnot set correctly, and hence the CPU 401 determines that it is notpossible to start reading the test chart. Therefore, the occurrence ofthe reading error is prevented. If the original table reading isperformed in this state, the first mirror unit 104 a and the secondmirror unit 104 b move to only the position of the A4 size because thetest chart is A4. Therefore, only a part of the test chart is read, andthe reading error occurs. In FIG. 17D, the case in which the test chartis set obliquely is illustrated. This state is caused by the fact thateven when the user sets the test chart correctly, the test chart istilted by a wind generated when the reader 200 is closed, for example.In this case also, the CPU 401 determines that it is not possible tostart reading the test chart. Therefore, the occurrence of the readingerror is prevented.

In FIG. 17E, the case in which an original different from the createdtest chart is set and a detected size of the original is different fromthe sheet size of the test chart is illustrated. In this case, the CPU401 determines that it is not possible to start reading the test chart.Therefore, the occurrence of the reading error is prevented. In FIG.17F, the case in which an original different from the created test chartis set and a detected size of the original is the same as the sheet sizeof the test chart is illustrated. In this case, the CPU 401 determinesthat it is possible to start reading the test chart. However, thereading error occurs after the original is read.

In a case where the sheet size of the test chart and the detectedoriginal size are the same as each other (S104: Y), the CPU 401determines that it is possible to start reading the test chart by thereader 200 (Step S105). Thus, for example, the CPU 401 switches thebutton 701 c for issuing an instruction to start the reading, which isincluded in the message screens 700 b and 700 c of FIG. 8B and FIG. 8C,from a grayed-out state to a state in which the button 701 c can bepressed. Alternatively, the CPU 401 switches a display from a messagescreen that does not include the button 701 c for issuing an instructionto start the reading to a message screen that includes the button 701 c.Thus, the display is switched from a state in which the user cannotissue an instruction to start the reading of the test chart to a statein which the user can issue an instruction to start the reading thereof.

When the button 701 c for issuing an instruction to start the reading ispressed and the instruction to start the reading is input, the CPU 401controls the operation of the reader 200 to perform the processing ofreading the test chart (Step S106). The CPU 401 executes the ADF readingin the case of the first reading mode, and executes the original tablereading in the case of the second reading mode. The CPU 401 executes theabove-mentioned calibration based on a result of reading the test chart,and completes the adjustment of the printing condition (Step S107).

FIG. 13B is a flowchart for illustrating processing for determiningwhether or not it is possible to start reading the test chart at atiming of receiving the instruction to start reading the test chart. Thesame step numbers are assigned to the same processing as the processingof FIG. 13A. A description of the same processing as that of FIG. 13A isomitted.

When the button 701 c for issuing an instruction to start the reading ispressed and the CPU 401, which has created the test chart in theprocessing of Step S102, receives the instruction to start the reading(Step S201), the CPU 401 executes the detection processing for theoriginal size by the reader 200 in Step S103. In a case where the sheetsize of the test chart created by the processing in Step S102 and theoriginal size detected by the processing in Step S103 are not the sameas each other (Step S104: N), the CPU 401 determines that it is notpossible to start the reading. In this case, the CPU 401 notifies theuser that the test chart is not set on the reader 200 correctly (StepS111).

FIG. 18A and FIG. 18B are exemplary illustrations of notificationscreens to be displayed on the display of the operating unit 400 in thiscase. In FIG. 18A, an example of a notification screen in a case wherethe ADF reading (first reading mode) is selected is illustrated. Thisnotification screen includes a notice that the test chart is not set onthe original tray 302 of the ADF 220 correctly, an instruction to resetthe test chart on the original tray 302, and an instruction to adjustthe regulating members 332, and the like. In FIG. 18B, an example of anotification screen when the original table reading (second readingmode) is selected is illustrated. This notification screen includes anotice that the test chart is not set on the original table glass 102correctly, an instruction to reset the test chart on the original tableglass 102, and an instruction to thrust and set the test chart againstthe original registration mark 1231.

After the notification, the CPU 401 repeatedly performs the processingof Step S201 and the subsequent steps until the sheet size of the testchart created by the processing in Step S102 and the original sizedetected by the processing in Step S103 are the same as each other. Forthis purpose, after the notification processing in Step S111, the CPU401 displays a screen, which includes the button 701 c for issuing aninstruction to start the reading, on the display of the operating unit400. The user presses this button 701 c through the operating unit 400,to thereby perform the processing of Step S201 and the subsequent steps.The notification in Step S111 may be performed by using an outputdevice, such as a sound output device or lamp display, as well as thedisplay of the notification screen on the display.

FIG. 13C is a flowchart for illustrating processing for determiningwhether or not to start reading the test chart at a timing of receivingthe instruction to start reading the test chart. FIG. 13C is an examplein which an order of the processing of Step S201 and the processing ofStep S103 in FIG. 13B are reversed. Each processing step is the samebetween FIG. 13C and FIG. 13B, and accordingly, a description thereof isomitted.

Hitherto, it has been required to determine the reading error from thereading result of the test chart, and accordingly, particularly in thecase of reading the test chart by using the ADF 220, time is wasteduntil the reading error occurs because the test chart is not setcorrectly. In contrast, the image forming apparatus 100 of at least oneembodiment determines whether or not the test chart is set correctlybefore the reading of the test chart is started, to thereby determinewhether or not it is possible to start reading the test chart. It is notpossible to start reading the test chart unless the test chart is setcorrectly, and hence the occurrence of the reading error caused by thefact that the test chart is not set correctly can be prevented. Theimage forming apparatus 100 can prevent a waste of rereading of the testchart, which is caused by the reading error. That is, such effects asshown in FIG. 16 are obtained.

Another Example of Determination as to Whether to Start Reading TestChart

In the above-mentioned processing for determining whether or not tostart reading the test chart, it is determined whether or not it ispossible to start reading the test chart based on whether or not thesheet size of the sheet used for the test chart and the original sizedetected by the reader 200 are the same as each other. However, theorientation of the test chart at the time when the test chart is read bythe reader 200 is sometimes limited depending on the type of theprinting condition to be adjusted by the test chart. In this case, theorientation of the test chart to be placed is included in such acondition for determining whether or not the sheet size and the originalsize are the same as each other.

For example, at the time of printing, the photosensitive drums 121, 131,141, and 151 are scanned in the main scanning direction (Y-direction) bythe laser beam. At this time, density unevenness sometimes occurs in themain scanning direction. The density unevenness in the main scanningdirection is caused, for example, by charge unevenness due to adeterioration of the charger 122 configured to charge the photosensitivedrums 121, 131, 141, and 151, exposure unevenness of the laser beam bythe exposure device 110, development unevenness by the developer 123, orthe like.

In the case of correcting such density unevenness in the main scanningdirection, test charts for density unevenness correction are created.FIG. 19A and FIG. 19B are explanatory diagrams of the test charts forthe density unevenness correction. In FIG. 19A, an example of a testchart 810 for the A4 size is illustrated. In FIG. 19B, an example of atest chart 811 for the A3 size is illustrated. In each of the testcharts 810 and 811, band-shaped test images formed of 50% densitysignals of the respective colors of yellow, magenta, cyan, and black areformed in the main scanning direction (Y-direction). Regardless of thesizes of the sheets, the band-shaped test images are formed so that themain scanning direction corresponds to a longitudinal direction of suchbands.

Reading of the test charts 810 and 811 for the density unevennesscorrection is performed so that the main scanning direction(Y-direction) of the test charts 810 and 811 is set to become parallelto the SX1-direction or SX2-direction of the reader 200. This is becausethe image sensor 105 includes photoelectric conversion elements arrayedlinearly side by side in the main scanning direction, andcharacteristics of the photoelectric conversion elements differdepending on positions thereof in the Y-direction. The reader 200performs the reading while setting the main scanning direction of thetest charts 810 and 811 to the SX1-direction or SX2-direction of thereader 200, to thereby be able to suppress a characteristic differencedue to the positions of the photoelectric conversion elements of theimage sensor 105.

Such a determination as to whether or not to start reading the testchart is performed similarly to the processing of Step S104 of FIG. 13Ato FIG. 13C. That is, the CPU 401 determines whether or not the sheetsize of the test chart created by the processing of Step S102 and theoriginal size detected by the processing of Step S103 are the same aseach other, and determines whether or not it is possible to startreading the test chart. At this time, the CPU 401 adds the orientationof the original to the determination condition regarding the match ofthe size. FIG. 20 is an explanatory table for determining whether or notit is possible to start the reading. The orientation of the original isadded to the determination condition regarding the match of the size. InFIG. 20, in a case where the sheet size is A4, it becomes possible tostart the reading for only A4R as the original size. In a case where thesheet size is A4 and the original size is A4, it is determined notpossible to start the reading because the orientation of the original isnot correct though the sheet size and the original size are the same aseach other. In this point, FIG. 20 is different from FIG. 14. In FIG.20, in a case where the sheet size is A3, it becomes possible to startthe reading for only the size of the original that is different from thefixed size. In a case where the sheet size is A3, a correct way ofplacing the test chart 811 is to set the test chart 811 on the originaltable glass 102 so that a part thereof lies off from the original table.Therefore, in the case of performing the density unevenness correctionby using the test chart 811 in which the sheet size is A3, it becomesimpossible to perform the reading in the ADF reading (first readingmode), and it becomes possible to perform only the reading in theoriginal table reading (second reading mode).

FIG. 21 is a table for showing a relationship between the set states ofthe test chart on the original tray 302 and results of reading the testchart. In this example, the orientation of the original is added to thedetermination condition regarding the match of the size, that is, theway of placing the original. Therefore, for the adjustment such as thedensity unevenness correction in the main scanning direction(Y-direction), in which the reading orientation of the test chart islimited, it is possible to prevent the occurrence of the reading errorwhen “the test chart is set at the fixed position and the readingorientation is not correct” as shown in FIG. 21.

Another Example of Determination as to Whether to Start Reading TestChart

A description is now given of an example in which, regardless of theorientation of the test chart, the test chart is placed so that thelongitudinal direction (long side of the sheet) of the test chartbecomes parallel to the Y-direction of the reader 200, to therebyprevent the occurrence of the reading error.

For example, in the case of “image failure diagnosis including detectionof ADF reading streak”, the test chart is placed so that thelongitudinal direction thereof becomes parallel to the Y-direction ofthe reader 200. FIG. 22A and FIG. 22B are explanatory diagrams of such atest chart for image diagnosis, which is used for “image failurediagnosis including detection of ADF reading streak”. The test chart 820for the image diagnosis includes: a white base portion 821 on which animage is not formed; and band-shaped test images 822, 823, 824, and 825formed of 50% density signals of the respective colors of yellow,magenta, cyan, and black. In FIG. 22A, an example of the test chart 820for the image diagnosis, which is formed on an A4 sheet, is illustrated.In FIG. 22B, an example of the test chart 820 for the image diagnosis,which is formed on an A4R sheet, is illustrated.

In the case of reading the test chart 820 for the image diagnosis,regardless of whether the test chart is A4 or A4R, it is required thatthe test chart 820 be set in the orientation in which the longitudinaldirection (long side of the sheet) thereof becomes parallel to theY-direction.

At the time of determining whether or not the ADF reading streak ispresent, in a case where streaks are detected in both which are beforethe test chart 820 is conveyed to the reading position of the reader 200and the white base portion 821 of the test chart, the streaks aredetected no matter whether or not the test chart 820 is present. In thiscase, it is determined that a streak caused by the reader 200 occurs.When the streak is not detected before the test chart 820 is conveyed tothe reading position of the reader 200, and the streak is detected onthe white base portion 821 of the test chart 820, it is determined thatthe streak is not such a streak caused by the reader 200 and is presenton the white base portion 821 of the test chart 820. In this case, it isdetermined that the streak is caused by the image forming apparatus 100.FIG. 23 is a table for showing a relationship between such streakdetection positions and the causes of the streak.

In order to classify the streak caused by the reader 200 and the streakcaused by the image forming apparatus 100, the image diagnosis isperformed for a wider reading region of the reader 200 in theY-direction. For this purpose, the test chart 820 is set in theorientation in which the longitudinal direction (long side of the sheet)thereof becomes parallel to the Y-direction. That is, the start of thereading is allowed only when the test chart 820 has the A4 size and isset on the reader 200.

FIG. 24 is an explanatory table for determining whether or not it ispossible to start the reading. In the case of the test chart 820 for theimage diagnosis, which includes the reading streak of the ADF,regardless of whether the sheet size is A4 or A4R, it becomes possibleto start the reading only when the original size is A4. Thus, it becomespossible to prevent the reading error when the test chart 820 for theimage diagnosis is placed in another way of placing the test chart 820.

As described above, at the time of adjusting the printing conditionthrough use of the test chart, the image forming apparatus 100 of atleast one embodiment determines whether or not the test chart is setcorrectly before performing the reading operation for the test chart.Thus, the reading error due to the work error of the user at the time ofcausing the reader 200 to read the test chart can be prevented fromoccurring. Therefore, it becomes possible to improve efficiency of theadjustment work using the test chart.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2019-088953, filed May 9, 2019, which is hereby incorporated byreference herein in its entirety.

1-5. (canceled)
 6. An image forming apparatus, comprising: a documentfeeder including a stacking tray on which a sheet is to be stacked, aconveying roller configured to convey the sheet stacked on the stackingtray, a discharging roller configured to discharge the sheet, and adischarge tray onto which the sheet is discharged by the dischargingroller; a reading unit including a reading sensor configured to read animage on the sheet conveyed by the conveying roller and a platen onwhich a sheet is to be placed, the reading sensor being configured toread an image of the sheet placed on the platen; an image forming unitconfigured to form an image based on an image forming condition; a sizesensor configured to detect a size of the sheet on the stacking tray;and a controller configured to: control the image forming unit to form atest chart on a sheet, receive user instruction information instructingto start reading the test chart, control the conveying roller of thedocument feeder to convey the sheet stacked on the stacking tray basedon the user instruction information, control the reading sensor to readthe test chart on the sheet while the conveying roller conveys thesheet, and generate the image forming condition based on a readingresult of the test chart by the reading sensor, wherein, in a case inwhich the user instruction information is received, the controllercontrols the conveying roller not to convey the sheet stacked on thestacking tray when the size of the sheet detected by the size sensor isnot the same as the size of the sheet having the test chart formedthereon.
 7. The image forming apparatus according to claim 6, whereinthe document feeder includes a regulating member configured to move in apredetermined direction to align the sheet stacked on the stacking tray,and wherein the size sensor detects the size of the sheet on thestacking tray based on a position of the regulating member in thepredetermined direction. 8-10. (canceled)
 11. The image formingapparatus according to claim 6, wherein the size sensor is provided atthe stacking tray and is configured to output a signal which changesdepending on a length of the sheet in a conveyance direction along whichthe conveying roller conveys the sheet.
 12. The image forming apparatusaccording to claim 6, wherein the size sensor includes a first sizesensor provided on the stacking tray and a second size sensor providedon the stacking tray, wherein the first size sensor is configured todetect a length of the sheet in a conveying direction along which theconveyance roller conveys the sheet, and the second size sensor isconfigured to detect a width of the sheet in a direction orthogonal tothe conveying direction.
 13. The image forming apparatus according toclaim 6, wherein the image forming unit includes a photosensitivemember, an exposure unit configured to expose the photosensitive memberwith a laser beam to form an electrostatic latent image on thephotosensitive member, and a developing unit configured to develop theelectrostatic latent image, wherein the test chart includes aband-shaped test image which extends in a main scanning direction inwhich the laser beam scans the photosensitive member, and wherein thecontroller is configured to generate, based on the read data, the imageforming condition to correct density unevenness in the main scanningdirection in an image formed by the image forming unit.
 14. The imageforming apparatus according to claim 6, wherein the image formingcondition is a conversion condition, and wherein the controller convertsimage data based on the conversion condition and controls the imageforming unit to form the image based on the converted image data. 15.The image forming apparatus according to claim 14, wherein theconversion condition is a tone correction condition.
 16. An imageforming apparatus, comprising: a document feeder including a stackingtray on which a sheet is to be stacked, a conveying roller configured toconvey the sheet stacked on the stacking tray, a discharging rollerconfigured to discharge the sheet, and a discharge tray onto which thesheet is discharged by the discharging roller; a reading unit includinga reading sensor configured to read an image of the sheet conveyed bythe conveying roller and platen on which a sheet is to be placed, thereading sensor being configured to read an image of the sheet placed onthe platen; an image forming unit configured to form an image based onan image forming condition; a size sensor configured to detect a size ofthe sheet on the stacking tray; and a controller configured to: controlthe image forming unit to form a test chart on a sheet, receive userinstruction information instructing to start reading the test chart,control the conveying roller of the document feeder to convey the sheetstacked on the stacking tray based on the user instruction information,control the reading sensor to read the test chart on the sheet while theconveying roller conveys the sheet, and generate the image formingcondition based on a reading result of the test chart by the readingsensor, wherein, in a case in which the user instruction information isreceived, the controller controls the reading sensor not to read theimage of the sheet when the size of the sheet detected by the sizesensor is not the same as the size of the sheet having the test chartformed thereon.
 17. The image forming apparatus according to claim 16,wherein the size sensor is provided at the stacking tray and isconfigured to output a signal which changes depending on a length of thesheet in a conveyance direction along which the conveying roller conveysthe sheet.
 18. The image forming apparatus according to claim 16,wherein the size sensor includes a first size sensor provided on thestacking tray and a second size sensor provided on the stacking tray,wherein the first size sensor is configured to detect a length of thesheet in a conveying direction along which the conveyance roller conveysthe sheet, and the second size sensor is configured to detect a width ofthe sheet in a direction orthogonal to the conveying direction.
 19. Theimage forming apparatus according to claim 16, wherein the image formingunit includes a photosensitive member, an exposure unit configured toexpose the photosensitive member with a laser beam to form anelectrostatic latent image on the photosensitive member, and adeveloping unit configured to develop the electrostatic latent image,wherein the test chart includes a band-shaped test image which extendsin a main scanning direction in which the laser beam scans thephotosensitive member, and wherein the controller is configured togenerate, based on the read data, the image forming condition to correctdensity unevenness in the main scanning direction in an image formed bythe image forming unit.
 20. The image forming apparatus according toclaim 16, wherein the image forming condition is a conversion condition,and wherein the controller converts image data based on the conversioncondition and controls the image forming unit to form the image based onthe converted image data.
 21. The image forming apparatus according toclaim 20, wherein the conversion condition is a tone correctioncondition.